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super_relate_consts do not spurriously fail on assoc consts

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Boxy 2022-11-24 08:36:28 +00:00 • committed by kadmin
parent 430f7d16e6
commit 4085e94ece
2 changed files with 29 additions and 16 deletions
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25
compiler/rustc_middle/src/ty/relate.rs
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@ -631,6 +631,15 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
b = b.eval(tcx, relation.param_env());
}
if tcx.features().generic_const_exprs {
if let Ok(Some(a2)) = tcx.expand_abstract_consts(a) {
a = a2;
}
if let Ok(Some(b2)) = tcx.expand_abstract_consts(b) {
b = b2
}
}
// Currently, the values that can be unified are primitive types,
// and those that derive both `PartialEq` and `Eq`, corresponding
// to structural-match types.
@ -647,22 +656,6 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
(ty::ConstKind::Placeholder(p1), ty::ConstKind::Placeholder(p2)) => p1 == p2,
(ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val,
(ty::ConstKind::Unevaluated(_), ty::ConstKind::Unevaluated(_))
if tcx.features().generic_const_exprs =>
{
// FIXME(generic_const_exprs): this spurriously fails when relating two assoc consts
// i.e. `<T as Trait>::ASSOC eq <T as Trait>::ASSOC` would return `false`. Wheras if
// both were behind an anon const that gets normalized away here it would succeed.
if let (Ok(Some(a)), Ok(Some(b))) = (
tcx.expand_abstract_consts(a),
tcx.expand_abstract_consts(b),
) && a.ty() == b.ty() {
return relation.consts(a, b);
} else {
false
}
}
// While this is slightly incorrect, it shouldn't matter for `min_const_generics`
// and is the better alternative to waiting until `generic_const_exprs` can
// be stabilized.